This pier type is constructed in place. Special equipment is required to drill a hole at an angle beneath the foundation, it makes use of a special device that expands the bottom of the hole, that is how it gets it’s name.
A steel framework is then place into the hole and it is then poured full of concrete. There is a waiting period while the concrete cures, usually seven days, before the foundation can be supported.
This pier type requires the greatest amount of soil removal, most of which must be hauled away. The Maximum depth of the piers holes is limited and in many instances may not reach deep enough past the affected soil to provide proper support.
Another issue with this method is the fact that the pier must be drilled at an angle sot the weight does not rest directly on top of the pier.
This type is sometimes installed before a foundation is poured but care should be taken to insure that the depth is great enough to reach stable soil providing proper support. Otherwise the foundation ends up with a large sinking weight attached to it.
1. Can be installed before the slab is poured.
2. Extremely high tensile strength
2. Extremely long installation times
3. Greatest Impact on areas near installation
4. Does not provide support directly beneath the foundation.